Cooling element and cooling device and method for their operation

ABSTRACT

An elongated right parallelepiped cooling element has a housing comprising a horizontal ceiling which forms a flat top surface which is about 2 mm below a room ceiling. Downward-projecting side parts, which hold a horizontal air-permeable wall at the bottom, connect to the ceiling. Arranged in the housing is an antechamber which is connected to an air connection and, at the top, has transverse slots distributed over its length. Air outlets distributed uniformly along a center line are arranged in the top surface. Beneath the ceiling, a pipe extends along an edge, through which pipe cooling liquid, possibly also heating liquid, can be passed. As a result, a room temperature in the comfort range can be maintained during working hours when the cooling air supply is always sufficient but not unnecessarily high. In addition, the room ceiling can be precooled without cooling air or even preheated outside working hours.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a cooling element according to the precharacterizing clause of claim 1, as used for cooling or generally for air-conditioning of rooms, in particular of office rooms and the like, and a cooling device which comprises such a cooling element and a method for its operation.

2. Description of the Related Art

WO-A-00/52 395 discloses a cooling element of the generic type which releases cooling air through an air-permeable wall at its bottom, which air flows downwards into the room to be cooled. However, the cooling effect achievable in this manner is not always sufficient, particularly in offices, since the cooling requirement is often very high owing to equipment which releases a great deal of heat. The instantaneous cooling requirement can then be so great during working hours that it can be covered only with difficulty by means of only the known cooling element of the generic type, especially if other boundary conditions, such as low air flow rates, a homogeneous temperature distribution and a low noise level, are also to be complied with.

Cooling elements can be supplemented by separate apparatuses for concrete core cooling, but this entails a high additional expense since pipes have to be laid in the ceiling and concreted in for this purpose. This can actually be done only during erection of the building, and subsequent laying of pipes for concrete core cooling is virtually ruled out. Moreover, the consequences of instantaneous heat load peaks can be reduced in this manner but cannot be compensated.

SUMMARY OF THE INVENTION

It is the object of the invention to further develop a cooling element of the generic type for a cooling device so that it is suitable for ensuring a sufficient cooling effect even at high heat loads without a cooling air supply substantially above that provided by the fresh air requirement being necessary. Moreover, it should enable the heat storage capacity of the room ceiling to be utilized in an economical manner without further measures.

The cooling element according to the invention permits the construction of a cooling device by means of which peaks in the heat load can be coped with without increasing the fresh air supply. Moreover, the storage capacity of the room ceiling can be utilized in a very simple manner for supplementing the cooling effect. As a result, the peak values of the instantaneous cooling requirement which has to be covered by the cooling element are substantially lower than would otherwise be the case.

In a particular development of the cooling element according to the invention, the cooling device can, if required, also be used at least partly for room heating. In this mode of operation, too, the storage capacity of the concrete can be utilized.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification. The invention is illustrated in more detail below with reference to Figures which merely represent embodiments. In the drawings,

FIG. 1 shows a bottom view of a first embodiment of a cooling element according to the invention, an air-permeable wall on the bottom being omitted,

FIG. 2 a shows a cross-section through the cooling element according to FIG. 1 along II-II,

FIG. 2 b shows the same cross-section through a cooling element according to a slightly modified second embodiment,

FIG. 3 shows a cut-out III from FIG. 2 a,

FIG. 4 a schematically shows a first embodiment of a cooling device according to the invention,

FIG. 4 b schematically shows a second embodiment of a cooling device according to the invention and

FIG. 5 shows a graph which illustrates a method, according to the invention, for operating a cooling device according to the invention.

DETAILED DESCRIPTION

A first embodiment (FIG. 1, 2 a) of the cooling element 1 according. to the invention comprises an approximately right parallelepiped elongated housing 2 which may be a few meters long and, for example, about 60 cm wide. In the example, it is composed of three housing sections 2 a,b,c whose cross-section in the longitudinal direction is constant and which are bent from sheet metal, e.g. aluminum sheet between 1.5 mm and 2 mm thick. The housing sections 2 a,b,c are identical, apart from the fact that the frontmost housing section 2 a has a closing end wall 3. In this way, housings of different lengths can be formed.

The housing 2 has, at the top, a horizontal flat ceiling 4 whose top forms a top surface 6 pointing towards a room ceiling 5 under which the cooling element 1 is suspended. The top surface 6 is between 1 mm and 5 mm, preferably about 2 mm, away from the room ceiling 5 so that an air gap is present between them. Adjacent to the sides are side parts which are bent downwards and comprise perpendicular side walls 7 a,b and, at the lower edge thereof, adjacent frame strips 8 a,b bent horizontally inwards and, at the inner edges thereof, fins 9 a,b bent perpendicularly upwards.

At the bottom, the housing 2 has a rectangular opening which extends over the entire length of the cooling element 1 and is closed by a horizontal air-permeable wall 10 (omitted in FIG. 1). The wall 10 is likewise composed of three cooling wall sections, each of which extends over one of the housing sections 2 a,b,c. The air-permeable wall 10 is adjacent to both lateral edges, preferably with its integral strips 11 a,b (cf. also FIG. 3) which project upwards and in each case become a hook profile 12 a,b which is curved outwards and whose concave, channel-like underside rests on the upper edge of the fin 9 a,b. This method of fixing the air-permeable wall 10 results in self-centering even in the event of deviations, caused by manufacturing tolerances, in the width thereof or in the spacing of the fins 9 a, 9 b from standard values or in the event of different variations in these dimensions due to thermal expansion. Moreover, the heat transmission between the housing 2 and the air-permeable wall 10 is low owing to the very small contact area. In addition, the wall can be inserted very easily and conveniently into the opening. It is also possible to provide a hook profile only on one side and to provide on the other side a flat retaining strip which rests with the underside on the fin.

The air-permeable wall 10 has small openings distributed over its entire area. It may be in the form of a cooling wall of sheet metal, preferably thin steel sheet and may have microholes of not more than 0.8 mm or better 0.6 mm, preferably about 0.5 mm, diameter, which are arranged, for example, in a square grid having spacings of about 5 mm. The proportion of the free cross-section can therefore be small, for example about 1% or less. A high coefficient of thermal conductivity, as possessed by thin steel sheet or aluminum sheet, is also advantageous. The air-permeable wall 10 can, however, also be in the form of perforated sheet metal, for example of aluminum having, for example, 16% free cross-section and 2.5 mm hole diameter, which is covered with a coated nonwoven, in which case it has a pronounced noise-damping effect. The openings are then determined especially by the structure of the nonwoven and are substantially smaller than stated for the cooling wall.

The ceiling 4 has air outlets 13 which are present in succession along a centre line in the longitudinal direction and may be in the form of round holes having a diameter of between 2 mm and 4 mm, e.g. 2.5 mm, which follow one another at the same distances of between 10 mm and 20 mm, e.g. about 15 mm, in the longitudinal direction.

The housing 2 and the air-permeable wall 10 enclose a chamber 14 in which is arranged an antechamber 15 which extends substantially over the entire length of the cooling element 1, has a rectangular cross-section and is separated from the remaining outer part of the chamber 14 by a partition 16 which encloses the antechamber 15 and, for example, consists of aluminum sheet. The partition 16 is mounted in the chamber 14 centrally and is at a distance both from the air-permeable wall 10 and from the ceiling 4. At the rear end, it has an air connection 17. At the top, it is penetrated by connecting openings which are in the form of transverse slots 18, follow one another in a regular manner in the longitudinal direction at a distance of between 50 mm and 150 mm, for example about 90 mm, and in each case have a width of not more than 2 mm or 1.5 mm, preferably of about 1 mm. Otherwise, the partition 16 is air-tight.

Mounted on the underside of the ceiling 4 is a pipe 19 for transporting a cooling liquid or heating liquid, usually cold or hot water, which pipe, in the housing sections 2 a,b,c consists in each case of sections of copper pipe 20 carried in heat-conducting rails 21 which are adhesively bonded to the ceiling 4, so that a good heat-conducting connection is ensured between the pipe 19 and the ceiling 4. The pipe sections are connected to one another and to connections by connecting hoses 22, for example plastic or metal hoses. The pipe 19 runs closely adjacent to one lateral edge of the ceiling 4 from the rear to the front end of the cooling element 1, from there to the opposite lateral edge and along this back to the rear end.

The air connection 17 is (FIG. 4 a) connected via a control valve 23 to an air supply pipe 24. The control valve 23 is controlled by a regulator 26, inter alia depending on the output signal of a measuring transducer 25 which measures the instantaneous air flow rate. The pipe 19 is operated as a cooling pipe. It is connected at one end to a cold water forward flow 27 and at the other end, via a control valve 28, which is likewise controlled by the regulator 26, to a cold water return flow 29. In this way, for example, a number of cooling elements which provide air-conditioning along a corridor of successive offices can be supplied from the corridor along which the air supply pipe 24, the cold water forward flow 27 and the cold water return flow 29 are led. The cooling element 1 then extends in each case from the corridor end up to close to the window end of the office.

The cooling device comprising the cooling element 1 and the room ceiling 5 can be operated during working hours, i.e. as a rule during the day, as shown in FIG. 5. The air flow rate L (solid line) and the cooling liquid flow rate K (dash-dot line) are shown as functions of the room temperature T_(i). Above a minimum operating temperature T_(min) of, for example, 22° C., cooling air at a cooling air temperature of between 10° C. and 15° C., preferably about 12° C., is passed into the cooling element 1 at a standard rate L_(n). The standard rate L_(n) corresponds to a value which can be set depending on the room size, the room load and the users' requirements and which may be, for example, between 60 m³/h and 120 m³/h. If the room temperature T_(i) exceeds the maximum operating temperature T_(max) of, for example, 26° C., which as a rule the room temperature should not exceed substantially, for example by not more than 1° C., the control valve 28 opens so that cold water at a temperature of, for example, 14° C. is passed into the pipe 19. If the room temperature T_(i) increases further, the control valve 28 is opened further.

The cooling liquid flow rate K may be, for example, a linear function of the room temperature T_(i) until it reaches its maximum value K_(max)

If the room temperature T_(i) falls below the minimum operating temperature T_(min), the control valve 23 is closed slightly and the air flow rate L is reduced in order to reduce the cooling. It may be, for example, a linearly decreasing function of the room temperature T_(i). The air flow rate L is, however, reduced at most up to a minimum air flow rate L_(min) of, for example, 30 m³/h, which still ensures a sufficient air supply, for example air exchange at least once or twice.

The cooling air flowing into the antechamber 15 at the cooling air temperature of about 12° C. via the connection 17 passes through the slots 18 into the chamber 14. Since the pressure drop along the antechamber 15 with its fairly large cross-section is very much smaller than the pressure difference between the antechamber 15 and the outer part of the chamber 14, which pressure difference is relatively large owing to the narrowness of the slots 18, the outflow through the slots 18 is virtually constant over the length of the cooling element 1 and the temperature of the cooling air, too, changes only slightly. The cooling air flows out of the chamber 15 for the most part through the air-permeable wall 10 into the room, where, because it is colder and heavier than the room air, it drops and easily penetrates the area of respiration of the users of the room. Since the air-permeable wall 10 is also cooled, it cools the room by radiant exchange also, in which it absorbs more heat than it releases. This contribution may be important particularly when the free cross-section of the air-permeable wall 10 is relatively small and its coefficient of thermal conductivity is large.

However, a part of the cooling air flows through the air outlets 13 in the ceiling 4 and between the top surface 6 and the room ceiling 5 to the lateral edges of the top surface 6, where it then likewise drops downwards along the side walls 7 a,b of the cooling element. On passing through the air gap, it absorbs any moisture from the room ceiling 5, while its temperature approaches the temperature thereof.

If cold water flows through the pipe 19, the ceiling 4 and the side parts of the cooling element 1 are cooled to a greater extent by heat-conducting contact therewith and contribute towards the cooling of the room. This takes place especially by direct radiant exchange with the room, but also by radiant exchange with the room ceiling 5, thermal conduction therein and radiant exchange between ceiling regions surrounding the cooling element 1 and the room and through contact between the cooling air which has emerged through the air outlets 13 and the top surface 6.

During an intermediate time which may comprise the entire time outside working hours, i.e. usually nights, cold water is, if required, passed through the pipe 19. As a result, in particular the ceiling 4 is greatly cooled and, through radiant exchange, over the top surface 6, cools the room ceiling 5, especially directly above the cooling element 1. Heat conduction within the room ceiling 5, however, also results in cooling of that region of the room ceiling 5 which surrounds the cooling element 1. The cooling of the room ceiling 5 could also take place entirely or partly through cooling air, but it is more economical to cool exclusively with cold water since air transport is relatively expensive and there is no fresh air requirement during the intermediate time.

The cooling is designed in such a way that the room temperature T_(i) at the end of the intermediate time and beginning of working hours corresponds approximately to the minimum operating temperature T_(min). The temperature of the room ceiling 5 is then also in this range or slightly lower, so that that region of the room ceiling 5 which is precooled by the cooling element 1 makes a substantial contribution to the cooling of the room during working hours, in particular in the vicinity of the cooling element 1, especially by direct radiant exchange with the room, and above the cooling element 1 by interaction with the cooling air which emerges through the air outlets 13 and, on flowing through the air gap between the room ceiling 5 and the top surface 6, remains relatively cool. Instead of cold water, in winter it is also possible to pass hot water as heating liquid through the water circulation and the pipe 19 (change-over operation), both during working hours and during the intermediate time. Owing to the possibly different heat load of the rooms, however, this is generally unsatisfactory.

In a second embodiment (FIG. 2 b) differing slightly from the first one, a second pipe 19′ which is otherwise identically formed is led parallel to the pipe 19 in an otherwise identically formed cooling element 1. The pipes 19 and 19′ are connected at one end to a cold water forward flow 27 or a hot water forward flow 27′, in particular via a control valve 28 and 28′, respectively, and at the opposite end to a cold water return flow 29 and a hot water return flow 29′, respectively.

If the room temperature T_(i) now falls below the minimum operating temperature T_(min), the control valve 28′ opens in addition to the reduction of the air flow rate L, so that hot water at a temperature of, for example, 35° C. is passed into the pipe 19′. The heating liquid flow rate H (dashed line in FIG. 5) is thus a—for example linearly—decreasing function of the room temperature T_(i) between the temperature at which said flow rate reaches its maximum H_(max) and the minimum operating temperature T_(min).

The housing 2 is heated by the heating liquid. Owing to the low heat transmission between the side parts and the air-permeable wall 10, this scarcely influences the latter so that the cooling air emerging through it is not heated too greatly and its temperature always remains below room temperature. On the other hand, the cooling air which has emerged through the air outlets 13 absorbs heat from the top surface 6 but is usually also not heated above room temperature. However, it is not troublesome if this case should occur, since it makes only a small contribution to the total air supply. The side parts of the cooling element 1 which are heated by the hot water, in particular the frame strips 8 a,b pointing downwards, heat the room directly by radiant exchange, while indirect heating by heat conduction and radiant exchange occurs via the room ceiling 5.

At low temperatures, heating liquid can likewise be passed through the pipe 19′ during the intermediate time, the heating liquid temperature and flow rate being chosen so that once again a room temperature which corresponds substantially to the minimum operating temperature T_(min) is reached at the end of the intermediate time. The room ceiling 5 is also slightly preheated, which reduces the heating required during working hours.

It is also possible to use a cooling element 1 according to the first embodiment (FIG. 1, 2 a) but simultaneously to provide both a cold water forward flow and return flow and a hot water forward flow and return flow and to connect the pipe 19 on one side via control valves to both forward flows and on the other side to both return flows, so that the pipe 19 can be connected alternatively to the cold water circulation or to the hot water circulation and performs substantially the same functions as the cooling element according to the second embodiment.

With the cooling devices and methods described, it is always possible to ensure a sufficient air supply on the one hand and, on the other hand, even in the case of a high cooling requirement, to set a room temperature which is in the comfort range of between 22° C. and 26° C. without the air supply having to assume values which are 

1. A cooling element comprising: a housing which is bounded at a top by a flat top surface and extends substantially over an entire length; an air-permeable wall which extends substantially over an entire length and is bounded in at least a part of the bottom in such a way that the housing and the air-permeable wall surround a chamber which has an air connection at a rear end; and at least one pipe for transporting a heating or cooling liquid, which runs inside the chamber from the rear end thereof substantially over an entire length to an opposite front end and back and is thermally coupled to the top surface.
 2. The cooling element according to claim 1, wherein the at least one pipe is mounted on the underside of a ceiling of the housing, the top of which forms the top surface.
 3. The cooling element according to claim 2, wherein the at least one pipe is arranged substantially at the lateral edges of the ceiling.
 4. The cooling element according to claim 1, further comprising two pipes which are preferably substantially parallel.
 5. The cooling element according to claim 1, further comprising air outlets distributed substantially over the entire length of the top surface and connected to the interior of the chamber.
 6. The cooling element according to claim 5, wherein the air outlets are arranged substantially along a center line of the top surface.
 7. The cooling element according to claim 6, wherein the air outlets follow one another at equal distances of, preferably, between 10 mm and 20 mm.
 8. The cooling element according to claim 5, wherein the air outlets are in the form of round holes, preferably having a diameter of between 2 mm and 3 mm.
 9. The cooling element according to claim 1, further comprising an antechamber, which is arranged inside the chamber, extends substantially over the entire length thereof, and is connected to the remaining outer part of the chamber by connecting openings distributed substantially over the entire length of said antechamber and at the rear end of which the air connection connects.
 10. The cooling element according to claim 9, wherein the connecting openings are mounted substantially at a top of the antechamber which is opposite the ceiling and a distance away therefrom.
 11. The cooling element according to claim 9, wherein the connecting openings have a width of not more than 2 mm, preferably not more than 1.5 mm.
 12. The cooling element according to claim 11, wherein the connecting openings are in the form of slots running in the transverse direction.
 13. The cooling element according to claim 9, wherein the connecting openings follow one another in the longitudinal direction, preferably at a distance of between 5 cm and 15 cm.
 14. The cooling element according to claim 9, wherein the antechamber has a substantially rectangular cross-section.
 15. The cooling element according to claim 2, wherein the housing comprises side parts which are adjacent to the ceiling on both sides and to which the air-permeable wall is fastened.
 16. The cooling element according to claim 15, wherein the air-permeable wall is substantially horizontal and the side parts have frame strips which are adjacent to the air-permeable wall on both sides in the manner of a frame.
 17. The cooling element according to claim 15, wherein the side parts comprise upward-projecting fins running in the longitudinal direction, and the air-permeable wall has, at at least one lateral edge, a hook profile which is concave in a downward direction, likewise runs in the longitudinal direction and grips over the upper edges of one of the fins.
 18. The cooling element according to claim 1, wherein the housing or each of a plurality of housing sections following one another in the longitudinal direction forms an integral bent part of sheet metal.
 19. The cooling element according to claim 1, wherein the cooling element is substantially in the form of a right parallelepiped.
 20. The cooling element according to claim 1, wherein the air-permeable wall is in the form of a cooling wall having micro-openings which are distributed over an area and have a diameter of not more than 0.8 mm, preferably not more than 0.6 mm.
 21. The cooling element according to claim 20, wherein the cooling wall includes sheet metal which is penetrated by the micro-openings.
 22. The cooling element according to claim 1, wherein the air-permeable wall is substantially in the form of a perforated metal sheet covered with a nonwoven.
 23. A cooling device comprising a cooling element according to claim 1, the cooling device also comprises a room ceiling to the underside of which the cooling element is fastened in a manner such that the top surface is a distance of between 2 mm and 10 mm from the underside of the room ceiling.
 24. A method for operating the cooling element according to claim 23, wherein air is passed at an air flow rate which is between a minimum rate and a standard rate into the cooling element during working hours, and cooling liquid is passed through the at least one pipe if the room temperature exceeds a maximum operating temperature.
 25. The method according to claim 24, wherein a flow rate of the cooling liquid in an interval lying directly above the maximum operating temperature is an ascending function of the room temperature.
 26. The method according to claim 24, wherein, during working hours, the air flow rate at a room temperature, which corresponds at least to the minimum operating temperature, corresponds to the standard rate and is reduced below the standard rate in each case when the room temperature falls below the minimum operating temperature.
 27. The method according to claim 26, wherein the air flow rate in an interval lying directly below the minimum operating temperature is a descending function of the room temperature.
 28. The method according to claim 24, wherein heating liquid is passed through the at least one pipe during working hours if the room temperature falls below a minimum operating temperature.
 29. The method according to claim 28, wherein the heating liquid flow rate in an interval lying directly below the minimum operating temperature is a descending function of the room temperature.
 30. The method for operating a cooling device according to claim 23, wherein cooling liquid or heating liquid is passed through the at least one pipe during an intermediate time outside working hours.
 31. Method The method according to claim 30, wherein the liquid temperature and liquid flow rate are chosen so that the room temperature at the end of the intermediate time substantially corresponds to the minimum operating temperature.
 32. The method according to claim 30, wherein no cooling air is passed into the cooling element during the intermediate time. 